Portable radio receivers and transceivers, such as wireless pagers, have become increasingly popular as a means of communication. Pagers are typically carried by users who wish or need to communicate when they are away from a telephone or computer, or are unable to predict where they may be reached at a given time.
In general, the user of a pager purchases the unit and enters into a contract with a service provider. As shown in FIG. 1, when someone 12 wishes to page a particular user, they contact the user's service provider 11, identify the user to be paged (perhaps with a personal identification number), and may give a message to the service provider 11 that is to be broadcast to the user's pager 15.
The service provider 11 maintains a network of radio transceiver base stations 13, 14 which are spread throughout the service area covered by the service provider. The transmitting base stations 13 are distributed so that transmissions from at least one base station can be received by a pager 15 anywhere in the service area.
In a simplistic system, when the service provider 11 receives a request to page a user 15, the page is broadcast by all the base stations 13 in the system. Thus, if the pager 15 is located anywhere in the service area, it will receive the page. The pager 15 will then alert the user that a page has been received with, for example, an audible or vibratory alert signal.
In a more sophisticated system, the pager 15 may have the capability to not only receive a transmission from the service provider's system, but may have the capability to transmit data back to the system. This is referred to as two-way paging.
Because the strength of a transmission from a pager 15 is tightly constrained by the battery power available to the pager, a two-way paging system must include a greater number of receiving base stations 14 than transmitting base stations 13. The receiving base stations 14 are smaller and distributed more widely than transmitting base stations 13 in order to receive the relatively weak transmissions broadcast by individual pagers 15. The receiving base stations 14 must be sufficient in number and distribution to receive pager transmissions originating anywhere in the service area.
With the advent of two-way paging, the pager user's ability to effectively communicate is limited only by the range of available messages the pager is capable of transmitting to the system. For example, to minimize equipment expense and power consumption, conventional two-way pagers may provide the pager user with a limited range of "multiple choice" responses to a page transmitted by the system. Alternatively, the pager may allow the pager user to initiate a transmission to the system from a limited list of pre-defined messages.
While more effective than merely receiving messages from the paging system, these methods obviously limit the pager user's ability to communicate. Accordingly, a need exists for a pager and paging system that provide the pager user with a much greater range of possible responses to a page or messages to be sent via the pager.